Musnad Ahmad 1167:3

Yunus narrated to us, he said: Layth—meaning Ibn Sa’d—narrated to us, from Hisham, from his father, from Asma’, the like of it. And he said: And she was a polytheist during the time of the Quraysh and their period [of truce], when they made a treaty with the Messenger of Allah, may Allah bless him and grant him peace.